RFR: 8238665: Add JFR event for direct memory statistics

[Alan Bateman]

On 13/03/2020 14:54, Denghui Dong wrote:
> Good suggestion, moved.
> Webrev: http://cr.openjdk.java.net/~ddong/8238665/webrev.03/
>
This looks much better.

What would you think about renaming the JFR event to 
"DirectBufferStatistics"? The concern I have with the proposed naming is 
that it will be really awkward to extend it to support mapped buffers.

The implementation changes look okay, hopefully Erik will skim over 
them. One small suggestion for for ManagementFactoryHelper is that you 
can stream().collect(Collectors.toList()) to create the value for 
bufferPools. You could even change it to volatile so that 
getBufferMXBeans isn't a synchronized method.

-Alan.